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Biodiversitäts-Forschung AFSV

Waldökologie, Landschaftsforschung und Naturschutz Heft 11 (2011) S. 49–61 4 Fig., 2 Tab. + Anh. urn:nbn:de:0041-afsv-01157

Impact of the admixture of European beech ( L.) on diver- sity and naturalness of conifer stands in Lower Saxony

Auswirkungen der Einbringung von Buche (Fagus sylvatica L.) auf die Artendiversität und Naturnähe von Nadelholzbeständen in Niedersachsen

Sabine Budde, Wolfgang Schmidt and Martin Weckesser

Abstract Buche (Fagus sylvatica) in standortsfremden Nadelholz- Monokulturen die Bedingungen im Sinne des Naturschutzes The promotion and extension of continuous cover mixed und der Forstwirtschaft verbessert. Diese Hypothese wird stands with a simultaneous reduction of conifer-monocultures auf der Grundlage von drei unterschiedlichen Nadelholz- play a major role in current silvicultural practices in Cen- Buchen-Versuchsreihen geprüft. Im Mittelpunkt steht dabei tral . It is assumed that the admixture of the natural die Bodenvegetation als wichtiger und sensitiver Indikator dominant beech (Fagus sylvatica) in pure non site-specific für den ökologischen Zustand von Wäldern. Jede Versuchs- conifer stands automatically indicates better conditions in reihe umfasst reine Nadelholz-Bestände (Picea abies, Pinus terms of nature conservation and forest management. To test sylvestris, Pseudotsuga menziesii), Nadelholz-Buchen- this hypothesis three different conifer-beech-comparisons of Mischbestände und reine Buchen-Bestände auf sauren pure and mixed stands in Lower Saxony are studied, analys- Mineralböden, auf denen von Natur aus nährstoffarme Buchen- wälder (Luzulo-Fagetum) vorherrschen würden. Das ing plant species diversity and naturalness of understorey Alter der Bestände variiert zwischen 50 und 150 Jahren. vegetation as one important indicator for the ecological Schwerpunkte der Analyse sind die Artenvielfalt und Naturnähe status of forests. Each comparison includes pure conifer- der Bodenvegetation. Um den Einfluss der Baumarten auf den ous stands (Picea abies, Pinus sylvestris, Pseudotsuga men- Standort und die Vegetation zu bewerten, werden die Licht- und ziesii), mixed coniferous-beech-stands, and pure beech stands Bodenverhältnisse der Bestände charakterisiert. on similar acidic mineral soils where the potential natural vegetation will be an oligotrophic beech forest (Luzulo- Es zeigt sich, dass mit der Beimischung der Buche in allen Versuchsreihen die Pflanzenartenvielfalt abnimmt und die Fagetum). The age of stands varies between 50 and 150 Naturnähe zunimmt. Unterschiedlich ist dabei die Intensität der years. To specify species influence on site conditions Veränderungen. Zwischen den Kiefern-Buchen-Mischbestän- and vegetation, the study also includes light climate and soil den und den Kiefern-Reinbeständen bestehen sehr deutliche data of the stands. Unterschiede im Aufbau der Bodenvegetation, so dass die It is observed that, with regard to all comparisons, the ad- Mischbestände den Buchen-Reinbeständen bereits sehr ähnlich sind. In den Douglasien- und Fichten-Versuchsreihen mixture of beech reduces plant species diversity but increases vollzieht sich der Artenwechsel vergleichsweise unauffällig naturalness of the stands. The intensity of beech admixture und kontinuierlich. Wenn man davon ausgeht, dass der effects differs. While in Scots stands the impact of ad- naturschutzfachliche und waldbauliche Status sich sowohl mixed beech is very noticeable, with the mixed stands being mit zunehmender Phytodiversität als auch bei zunehmen- nearly identical with pure beech stands, the species change der Naturnähe verbessert, so zeigen diese Ergebnisse auf in Douglas- and Norway stands proceeds more Bestandesebene eine gegenläufige Entwicklung, da das in slowly. der Region der potenziell natürlichen Vegetation entspre- chende Luzulo-Fagetum von Natur aus sehr artenarm Assuming that the status in nature conservation and forest an Gefäßpflanzen ist. management is improving with increasing plant species diver- sity and increasing naturalness, the results of this study show Schlüsselwörter: Bodenvegetation, Luzulo-Fagetum, a contrary development on a stand scale, as the potential Picea abies, Pinus sylvestris, Pseudotsuga menziesii, Humus- natural vegetation of the L u z u l o - F a g e t u m is in its self akkumulation, Licht, pH-Wert, Naturschutz very species poor on vascular . 1 Introduction Keywords: Understorey vegetation, Luzulo-Fagetum, Picea abies, Pinus sylvestris, Pseudotsuga menziesii, humus In the 19th century in many parts of Central Europe there was widespread reforestation on degraded soils with non- accumulation, light, pH-value, nature conservation autochthonous coniferous tree species, such as Scots pine (Pinus sylvestris) or Norway spruce (Picea abies). These Zusammenfassung species were favoured because they were easy to establish Die Förderung und Ausweitung von Mischwäldern bei gleichzei- and to manage, and because these fast growing species tiger Reduktion reiner Nadelholz-Bestände spielt aktuell eine appeared to provide a solution to significant timber shortage große Rolle im mitteleuropäischen Waldbau. Gemeinhin wird at this time (Sp i e c k e r 2003). Driven by a similar motivation angenommen, dass die Beimischung der standortsgemäßen for fast growing and high yielding timber crops, non-native

Waldökologie, Landschaftsforschung und Naturschutz 11 (2011) 49 AFSV Biodiversitäts-Forschung

Douglas-fir Pseudotsuga( menziesii) has also been introduced Lower Saxony (forest growth zone “Mitteldeutsches Trias-Berg- into many parts of Central Europe more recently (Ko w a r i k und Hügelland”, Ga u e r & Al d i n g e r 2005) and rise to 528 m 2010, Ko w n a t z k i et al. 2011). above sea level. The research area is characterized by a humid, sub-montane to montane climate (latitude: 51°40’ N–51°50’N, Today the use of these fast growing monocultures is still very longitude: 9°26’E–9°44’E, elevation: 300–450 m NN, annual common, but it is intensely debated because of their potential precipitation: 915–1,030 mm, mean annual temperature: instability and their negative impacts on biodiversity (Sp i e c k e r 7.3 –7.8°C, Ga u e r & Al d i n g e r 2005). The parent rock of the 2003). A high level of biodiversity is thought to increase Solling plateau is red sandstone covered with loess. Therefore ecosystem stability, at least with respect to the diversity of the main soil type is an acid silty loam cambisol (FAO clas- overstorey tree species (Sc h ü t z 2001, Sc h e r e r -Lo r e n z e n et sification) with a high content of aluminium but a good water al. 2005, Rö h r i g et al. 2006, Ba r b i e r et al. 2008, Pa q u e t t e & e c k e ss e r Me ss i e r 2011). Large-scale conversion of the existing even- supply (W 2003, with further details and maps of the aged coniferous stands into continuous cover mixed stands is research area and investigated stands). recognised as a solution to improve forest ecosystem stability and biodiversity. The main broadleaved tree species used in Investigations in the regions cover a much wider many forest conversions at present is European beech (Fagus geographic range, including three different forest growth sylvatica), which is one of the dominant native tree species of zones. The northernmost part is the coastal area of Lower Central European forests (Bo h n & Ne u h ä u sl 2000/2003). Saxony (forest growth zone “Niedersächsischer Küstenraum”, latitude: 53°24’ N–53°29’N, longitude: 9°00’E–9°20’E, eleva- Many studies have found unfavourable effects of conifer tion: 0–75 m NN, annual precipitation: 715–840 mm, mean plantations on vegetation, humus, soil etc. when compared annual temperature: 8.4–9.0°C, Ga u e r & Al d i n g e r 2005). to pure broadleaf stands (Norway spruce: Ze r b e 1994, Hü t t l Following a climatic gradient from the northwest to & Sc h a a f 1995; Douglas-fir: Kn o e r z e r et al. 1996, Ma r q u e s the more sub-continental affected southeast, the west-central & Ra n g e r 1997; Scots pine: Ze r b e et al. 2000, Au g u s t o et al. lowlands of Lower Saxony (forest growth zone “Mittelwestnied- 2002). Fewer studies have explicitly considered how conifer- ersächsisches Tiefland”, latitude: 52°33’ N–53°18’N, longitude: broadleaf mixtures influence biodiversity or site conditions 8°30’E–9°40’E, elevation: 75–150 m NN, annual precipitation: (Spruce/beech: Lü c k e & Sc h m i d t 1997, Ma t t h e s 1998, Le i t l 650–810 mm, mean annual temperature: 8.5–9.3°C, Ga u e r & 2002, Gä r t n e r 2003, En g e l h a r d & Re i f 2004, Gr o d z i ń s k a et Al d i n g e r 2005) have a slightly lower annual precipitation and al. 2004, Sc h m i d t et al. 2004; Douglas-fir/beech: Vo r & Sc h m i d t a higher mean annual temperature. Finally, at the end of the 2006; Pine/beech: Sc h m i d t et al. 2004, Vo r & Sc h m i d t 2006, climatic gradient the eastern lowlands of Lower Saxony (forest De n n e r & Sc h m i d t 2008). The main objective of these stud- ies is often the analysis of biodiversity. The discussion of the growth zone “Ostniedersächsisches Tiefland”, latitude: 52°39’ results in context with naturalness or ecosystem functions is N–53°28’N, longitude: 9°45’E–10°40’E, elevation: 30–170 mostly lacking. m NN, annual precipitation: 560–810 mm, mean annual tem- perature: 8.1–9.1°C, Ga u e r & Al d i n g e r 2005) are situated. The It is assumed that stands of native forest automatically entire Pleistocene region is formed by glacial sedimentary entail a higher naturalness of the associated biotic communi- deposits resulting in sandy soils partly covered with loess. ties (Fr i t z 2006, Re i f & Wa l e n t o w s k i 2008). However, at least The main soil type is the fresh sandy podsol-cambisol (FAO regarding understorey vegetation of managed mixed forests, classification) with low base saturation and not influenced by this assumption is lacking scientific proof. Our study compares a high groundwater table (Bu d d e 2006, also with further details plant species composition, species diversity, and occurrence and maps of the research area and investigated stands). of forest species of pure coniferous, mixed coniferous-beech, and pure beech stands in Lower Saxony, based on two similar The potential natural vegetation in both regions would be the studies by We c k e ss e r (2003) and Bu d d e (2006). To enable a Luzulo-Fagetum (Ge r l a c h 1970, He i n k e n 1995, Ell e n b e r g better understanding for the underlying mechanisms, light, & Le u s c h n e r 2010). In the Middle Ages at the latest natural humus morphology, and soil acidity are also compared. The aim beech forests have been largely replaced by arable fields and of this study is to find answers to the following questions: meadows on more fertile soils, and by heathlands and pastures on less fertile soils. Remaining forests have been grazed and 1. Are plant species diversity and naturalness influ- enced by the admixture of beech to coniferous managed for the production of fuel and charcoal. Around plantations? 200–250 yrs. ago the devastated areas were converted into 2. Does a site factor change by the admixture of large monocultures of conifer (Ge r l a c h 1970, Kr e ms e r 1990). beech to coniferous stands which then might While Scots pine is at least considered native in a few parts explain a change in understorey vegetation? of the lowlands (He sm e r & Sc h r o e d e r 1963, He i n k e n 1995), Norway spruce is not in regard to the Solling Mountains The results and discussion will show how these ecological (Fi r b a s 1952, Sc h m i d t -Vo g t 1987). Present-day forest stands interactions are influenced by the admixture of beech in conifer- are still dominated by these conifer species. Scots pine cov- ous stands and, whether they are as favourable as assumed ers 27–45 % of the total forest area in the three investigated in terms of silviculture and nature conservation. growth zones of the lowlands, while in the Solling Mountains Norway spruce occupies approximately 60 % of the forested 2 Material and methods area (Ga u e r & Al d i n g e r 2005). Since the Second World War there is a tremendous increase in planting of exotic Douglas- 2.1 Research area fir mainly caused by decreasing prices of Douglas-fir seeds The study sites are located in two separate areas of Lower and saplings (Ko w n a t z k i et al. 2011). Current forest planning Saxony (north-western ). These are within the Solling allots up to 10 % of the forest area for long-term Douglas-fir Mountains and the Pleistocene regions of Lower Saxony. The silviculture in Lower Saxony, mainly in mixture (Kl e i n s c h m i t Solling Mountains belong to the mountain ranges of southern 1991, Ko w a r i k 2010).

50 Waldökologie, Landschaftsforschung und Naturschutz 11 (2011) Biodiversitäts-Forschung AFSV

2.2 Sampling methods and analysis presence-absence relationship between the number of spe- cies of two stand types and the total number of species. For In both study areas pure coniferous and beech stands were quantitative purposes the percent similarity index was used compared with mixed stands. One study delivers vegetation (Cz e k a n o w s k i 1909, cited by Go o d a ll 1973), based on con- data on Norway spruce with beech in the Solling Mountains stancy (number of relevés within one stand type in which a (We c k e ss e r 2003), the other on Douglas-fir with beech, and given species occurs, Di e r s c h k e 1994). Both DCA and similarity Scots pine with beech in the Pleistocene lowlands (Bu d d e indices include all species of the herb and moss layer. 2006). To enable a better comparison within the two stud- ies, 20 plots (400 m2) of each stand type (Solling Mountains: The relative irradiance was measured on homogeneously pure spruce, pure beech, spruce/beech mixture, Lowlands: clouded days directly above the herb layer with PAR sensors pure pine, pure Douglas-fir, pure beech, pine/beech mixture, (type Licor S190). 36 (lowlands) and 40 (Solling) measure- Douglas-fir/beech mixture) have been selected for this analysis. ments per plot (each lasting two seconds) have been related Criteria for the selection of stands included stand age (> 50 and to continuous data recorded at a reference outside the forest < 150 years), canopy cover of > 50 % and, in mixed stands, (He i n k e n 1995). For measuring the thickness and soil acidity the proportions of the beech-conifer mixture was restricted to of the humus layer 12 soil samples (25 x 25 cm by using a a coverage of at least 40 % coverage for either tree species. metal frame) were taken per plot. In the lowland plots humus The wide range of stand age is due to the fact, that some tree samples were separated into OL(organic litter layer) and species, like Douglas-fir, reach high productivity and maturity OF/OH (decomposing organic layer) horizons while in the Solling more early than other. Furthermore, many of the Douglas-fir plots the humus layer was not separated. For pH analysis in stands have been established not before the Second World KCl, all 12 fresh samples of each plot were combined to form War (Ko w n a t z k i et al. 2011). To minimize influence of stand a mixed sample. age on results, chosen stands should be more or less in their optimum of tree layer coverage and wood productivity. All Because the investigated stands appeared to be very diverse plots were situated in managed forests, but no management and heterogeneous, tests for a normal distribution of the data activities took place in the last three years prior to the start failed. Accordingly, the non-parametric Kruskal-Wallis test was of field research. applied for the comparison between the forest types. The level of significance was set at p ≤ 0.05. Statistical analyses were Vegetation was assessed within the 400 m² plots in tree (≥ 5 m done using St a t i s t i c a 6.1 (St a t So f t , Inc. 2004). height), shrub (woody plants: 0.5–5 m height), herb (woody plants: < 0.5 m, all ferns, grasses, herbs), and moss layer at 3 Results the peak of the vegetation period (June, July). Visual estimates of the percentage cover of each of the species present were 3.1 Vegetation structure and diversity recorded in each of these different strata (Di e r s c h k e 1994). The nomenclature for vascular plants followed Wi ss k i r c h e n & Results are always shown in separate comparisons according Ha e u p l e r (1998) and for the bryophytes Ko p e r s k i et al. to the three coniferous tree species. Concerning percentage (2000). cover of vegetation layers (Tab. 1) all three comparisons coincide more or less in their results. Highest coverages of Alpha-diversity was calculated for each study plot including tree layer are found in the pure beech stands, accompanied all species in the herb and moss layers. Degree of natural- by low coverages of ground vegetation. In pure conifer stands ness was assessed by species occurring only in the herb the relations are vice-versa (exception: herb layer of Norway layer using a method developed by Sc h m i d t et al. (2003): this spruce stands). method provides an affinity value for every species for differ- ent forest habitats. The relative proportions of these so-called Within the Douglas-fir and Scots pine comparisons an evident forest species as well as the non-forest species in each plot influence of admixture of beech to coniferous species exists. is used as an indicator of naturalness. Facilities and limits Percentage covers of bryophytes and herbs show an obvious of this approach are discussed by Sc h m i d t et al. (2004) and depression in mixed stands that do not differ significantly from Sc h m i d t & Sc h m i d t (2007). pure beech forests. In contrast to this, the coverage of the moss layer in mixed stands of spruce and beech is as high Any differences in vegetation species composition between as in pure spruce stands. study plots were calculated and visualized by Detrended Correspondence Analysis (DCA) with Pc Ord (McCu n e & In each of the three types of pure coniferous stands, a higher Me f f o r d 1999). Additionally, two different indices were applied species diversity of herbs and mosses was found than in pure to illustrate vegetation similarity between pure and mixed beech forests (Fig. 1). Nevertheless, admixture of beech to stands: For a qualitative approach the Sø r e n s e n coefficient coniferous species does not necessarily have a negative (Sø r e n s e n 1948, cited by Di e r s c h k e 1994), based on the influence on plant species diversity as mean species numbers

Tree layer (%) Shrub layer (%) Herb layer (%) Moss layer (%) Tab. 1: Coverage of vegetation layers Mean ±SE (Median) Mean ±SE (Median) Mean ±SE (Median) Mean ±SE (Median) (n = 20, plot size = 400 m²). Douglas-fir Means that do not share the 77,8 2,2 (77.5) a 1,1 0,5 (0.1) a 31,0 6,7 (23.8) a 30,5 5,0 (22.5) a Mixed 89,8 2,4 (91.3) b 0,8 0,3 (0.1) a 6,6 2,1 (1.7) b 1,9 0,9 (0.2) b same letter differ significantly Beech 94,4 1,5 (96.3) b 0,2 0,1 (0.0) a 15,6 6,8 (0.3) b 0,2 0,0 (0.1) b (Kruskal-Wallis test, p < 0.05). Norway spruce Spruce 72,5 1,0 (73.8) a 0,0 0,0 (0.0) a 8,3 1,7 (4.8) a 7,9 1,3 (5.1) a Tab. 1: Deckungsgrade der Vegetations- Mixed 77,5 1,4 (75.6) a 1,3 0,5 (0.0) a 16,5 3,3 (13.0) a 5,9 1,0 (5.0) a schichten ( n = 20, Aufnahme- Beech 85,5 1,4 (87.5) b 0,1 0,0 (0.0) a 11,1 2,8 (8.4) a 0,5 0,1 (0.3) b fläche = 400 m2). Kleinbuch- Scots pine staben kennzeichnen signifikante Pine 58,0 1,2 (57.5) a 4,9 1,9 (2.0) a 96,1 1,0 (97.5) a 72,0 5,3 (78.8) a Mixed 94,0 1,4 (96.3) b 0,6 0,3 (0.0) b 7,0 3,1 (0.3) b 0,7 0,3 (0.1) b Unterschiede zwischen den Mit- Beech 94,4 1,5 (96.3) b 0,2 0,1 (0.0) b 15,6 6,8 (0.3) b 0,2 0,0 (0.1) b telwerten (Kruskal-Wallis-Test p < 0.05).

Waldökologie, Landschaftsforschung und Naturschutz 11 (2011) 51 AFSV Biodiversitäts-Forschung

Fig. 1: Species number per plot (400 m2, n = 20) for herb and moss layer, including all species. The solid line indicates median, the dotted line mean value, n = 20. Figures below the box plots show cumulative species richness in each stand type. Means that do not share the same letter differ significantly (Kruskal-Wallis test, p < 0.05).

Abb. 1: Zahl der Arten in der Kraut- und Moosschicht pro Aufnahmefläche (400 m², n = 20). Die durchgezogene Linie bezeichnet den Median und die gepunktete den Mittelwert. Die Ziffern unterhalb der Boxplots geben die kumulative Artenvielfalt für jeden Bestan- destyp wieder. Unterschiedliche Buchstaben kennzeichnen signifikante Unterschiede (Kruskal-Wallis-Test, p < 0.05). in mixed stands of beech and spruce (20 herbs, 13 mosses) Scots pine stands is mainly a result of a changing proportion of do not differ significantly from numbers found in pure spruce regenerating tree species. On the other hand, it must be taken stands (19 herbs, 11 mosses). In contrast to this, species into consideration that according to the absolute number of diversity in mixed forests of pine and beech (7 herbs, 5 mos- species (Fig. 2) both categories show decreasing trends from ses) is as low as in pure beech stands (9 herbs, 5 mosses). pure conifer to pure beech stands, simply because species Furthermore, in mixed stands of Douglas-fir and beech the diversity is decreasing in general (see previous chapter). herb layer diversity (15) has an intermediate position between the pure stands (Douglas-fir 21, beech 9) whereas the number of moss species is as low as in the pure beech stands. 3.3 Similarity In the Douglas-fir and Norway spruce comparisons, composi- Cumulative species richness in each stand type (Fig. 1) cor- tion of vegetation in mixed stands has a greater similarity with roborates these findings. While mixed stands of spruce and coniferous stands than with beech stands (Tab. 2). However, beech, with a total of 62 herbs show a similar diversity to pure spruce stands (64) concerning the herb layer, mixed stands mixed stands with pine and beech have a greater affinity of Douglas-fir and beech have an intermediate position (both towards pure beech stands than towards pure pine stands. herb with 71 species and moss layer with 18 species). As for Similarity is actually lowest between mixed stands and pure the Scots pine comparison mixed stands even present the pine stands. This suggests an absolute dominance effect of lowest diversity in the herb layer (40). beech trees in the mixed stands.

Tab. 2: Similarity coefficients based on presence-absence S( ø r e n s e n - 3.2 Naturalness index, calculated following Di e r s c h k e 1994) or constancy For comparison of biological diversity, which is one of the (percent similarity-index, calculated following Di e r s c h k e main aims of nature conservation, it is important not only to 1994) of all species of the herb and moss layer within each determine α-diversity for the different stand types, but it is stand type. rather necessary to differentiate between plants that are typical Tab. 2: Ähnlichkeitskoeffizienten S ( ø r e n s e n -Index: Vorkommen/ for a certain habitat and which are not. Following the “list of Nicht-vorkommen; Percent similarity-Index: Vorkommen vascular forest plant species” of Sc h m i d t et al. (2003) in the mit Berücksichtigung der Stetigkeit, jeweils unter Anwen- Lowlands (Douglas-Fir, Scots pine) over 50 % of the species dung der Formeln bei Di e r s c h k e 1994) unter Einschluss in the herb layer are plants growing predominantly in forests, aller Arten der Kraut- und Moosschicht innerhalb eines summarized as “Category 1” (Fig. 2). As for the Solling sites Bestandestyps. (Norway spruce) ratios of forest plants (Cat. 1) and plants which are not predominantly linked to forest (Cat. 2) are just Douglas-fir Norway spruce Scots pine the other way around. Not even the beech stands in the Solling Sørensen Mountains reach a percentage of 40 % forest plants. Be M ix Be M ix Be M ix M ix 66.7 M ix 60.6 M ix 60.7 If the comparisons are viewed with respect to the influence Dou 69.0 72.5 Spr 58.6 72.4 Pi 60.3 53.2 of beech on coniferous stands, there is always an increasing Percent similarity percentage of typical forest plants with the admixture of beech. Be M ix Be M ix Be M ix In relation to Norway spruce and Scots pine, this beech effect M ix 66.6 M ix 55.1 M ix 60.8 is much clearer than in Douglas-fir, whereas the shifting in the Dou 53.2 66.9 Spr 47.1 74.9 Pi 42.1 38.3

52 Waldökologie, Landschaftsforschung und Naturschutz 11 (2011) Biodiversitäts-Forschung AFSV

Fig. 2: Percentages of forest plants (herb layer, all species) based on means of qualitative analysis of vegetation relevés (n = 20, plot size = 400 m²). Figures beside the bars show mean absolute numbers of species per plot relating to categories 1 and 2.

Abb. 2: Qualitatives Waldartenspektrum der Krautschicht in den verschiedenen Bestandestypen (n = 20, Flächengröße 400 m²). Die Ziffern neben den Balken geben die mittleren Artenzahlen pro Fläche für die Kategorien 1 und 2 wieder.

The qualitative interpretation with Sø r e n s e n (1948, cited in pure beech stands are also found in the mixed and pure by Di e r s c h k e 1994) as well as the percent similarity index coniferous stands enriched by species typical to coniferous (Cz e k a n o w s k i 1909, cited by Go o d a ll 1973) generally indicate forests (e. g. Vaccinium myrtillus, Trientalis europaea, Dicranum high similarities between the stand types, nearly always more scoparium) and forest gaps (e. g. Epilobium angustifolium, than 50 %. Luzulo-Fagetum could therefore be under- Rubus spec.). stood to form the potential natural vegetation even in most of the studied pure coniferous stands. Differences between both Another influencing factor which is worked out by the ordina- indices occur when pure beech stands are considered. For tion is the site dependency. The second axis (eigenvalue 0.23 and length of gradient 2.56) clearly differentiates the stands all three comparisons they show about the same similarity from the Solling region from those in the lowland region. But towards the mixed stands and towards the pure conifer- also a more compact arrangement is visible within the Solling ous stands in terms of the Sø r e n s e n coefficient. When the stands, which points at more homogenous stands compared frequency of species occurrence in the stand types is included to the Lowland stands. This may be a matter of tree species (percent similarity index) similarity towards mixed stands is (Norway spruce), but it is more likely that this effect is caused clearly higher than towards pure coniferous stands, especially by the different geographic extent of the two study sites. concerning the pine stands.

If coverage of species is considered, similarity of stand types 3.4 Light climate, humus accumulation and shows a quite distinct pattern referring to the ordination diagram soil acidity (Fig. 3). The first axis (eigenvalue 0.34 and length of gradient The main environmental variables affecting vegetation are 2.98) separates corresponding pure beech stands from pure light and soil. In order to reduce soil variables, only the humus coniferous stands, with the mixed stands always showing an accumulation and pH-values of the organic layer are analysed intermediate position. as the most representative factors.

Beech and pine stands show the greatest distance in regard In all of the three comparisons relative irradiance measured to species composition. Most differentiating species in the on the forest floor was very low in beech stands (2.1 % and herb layer, serving as main variables for the first axis, are 2.8 %) and differs significantly from pure conifer stands Fagus sylvatica with a strong positive correlation (r = 0.62) and (Fig. 4). Within the conifer stand types, maximum irradiance Deschampsia flexuosa (r = -0.76) or Vaccinium myrtillus values are found in the pine stands, presenting a mean value (r = -0.73) with a negative correlation. All differentiating species of 25.3 %. For the mixed stands a strong impact of beech on with a negative correlation have a high frequency and coverage the light climate is obvious in the admixture with Douglas-fir in the pure pine stands (Tab. 3 Appendix). Table 3 also shows as well as with pine. With relative irradiance values of 3.5 % that within the comparison of pure coniferous stand – mixed (Douglas-fir-beech) and 2.1 % (Scots pine-beech) they do stand – pure beech stand a qualitative change of the species not show significant differences to the pure beech forests. In pool does not take place. Almost all plant species occurring contrast to this, relative irradiance in mixed stands of spruce

Waldökologie, Landschaftsforschung und Naturschutz 11 (2011) 53 AFSV Biodiversitäts-Forschung

Fig. 3: Ordination diagram based on DCA of plots (plot size = 400 m²) in different stand types. Cover of species was squareroot-trans- formed. Arrows indicate the most important species according to a Pearson correlation coefficient r ≥ 0.60, Desfle:Deschampsia flexuosa, Dicsco: Dicranum scoparium, Fagsyl: Fagus sylvatica, Hypcup: Hypnum cupressiforme (includes H. jutlandicum in the lowlands), Quespe: Quercus spec., Plesch: Pleurozium schreberi, Vacmyr: Vaccinium myrtillus.

Abb. 3: DCA-Ordinationsdiagramm der Aufnahmen (Aufnahmefläche 400 m²) in den verschiedenen Bestandestypen. Der Deckungsgrad wurde einer Wurzeltransformation unterzogen. Pfeile zeigen die wichtigsten Arten mit einem Pearson-Korrelationskoeffizienten r ≥ 0.60. Desfle: Deschampsia flexuosa, Dicsco: Dicranum scoparium, Fagsyl: Fagus sylvatica, Hypcup: Hypnum cupressiforme (im Tiefland einschließlichH. jutlandicum), Quespe: Quercus spec., Plesch: Pleurozium schreberi, Vacmyr: Vaccinium myrtillus. and beech (5.9 %) does not differ significantly from the values Compared to pure beech forests, the three pure conifer stand measured in the pure spruce stands (5.6 %). types are generally characterized by lower pH values in the humus layer (Fig. 4). pH-values in the Solling Mountains are In each of the three comparisons, the humus layer is thickest generally lower, on average 3.0 in the pure spruce stands, up in the mixed stands (Fig. 4). In the Douglas-fir comparison, to 3.7 in the pure beech stands. In the lowlands, beech stands the lowest humus accumulation is found in the conifer stands, show pH-values of nearly 4 (OF/OH-horizon) and at least 3.6 in whereas in the Norway spruce comparison, humus accumula- the conifer stands. Mixed stands, especially with spruce and tion is at its lowest in the pure beech stands. Within the Scots Douglas-fir, show a greater affinity with pure conifer stands pine comparison, pure stands do not differ from each other. than with beech stands. In the OL-horizon a considerable Generally, humus accumulation in the Solling Mountains does influence of the beech litter on soil acidity can be shown only not exceed a depth of 6 cm, whereas all plots in the lowlands for the mixed stands with Scots pine, as pH-values do not are at least 5 cm deep (pure Douglas-fir) and in most stand differ from those measured in pure beech plots. In the OF/ types about 8 cm. With a depth of nearly 12 cm, the mixed OH-horizon this effect is not obvious. stands of Scots pine and beech have the greatest accumula- tion of all the stands.

54 Waldökologie, Landschaftsforschung und Naturschutz 11 (2011) Biodiversitäts-Forschung AFSV

Fig. 4: Thickness and pH-value (KCl) of the

litter layer (OL), decomposed humus

layer (OF/OH), and relative irradiance for the herb layer. n = 20 except for the Solling site (soil data: Spr 13, Mix 8, Be 16, irradiance: Spr 13, Mix 14, Be 16) and irradiance in the lowlands (Dou 11, Dou-Be 11, Be 9, Pi 9, Pi-Be 14), plot size = 400 m²; means that do not share the same letter differ significantly (Kruskal- Wallis test, p < 0.05).

Abb. 4: Mächtigkeit und pH-Wert (KCl) der Humusauflage (unzersetzte Streu-

schicht OL), zersetzte Humusauflage

(OF/OH)) und relativer Lichtgenuss der Krautschicht. n = 20 mit Ausnahme der Flächen im Solling (Bodendaten: Fi 13, Fi-Bu 8, Bu 16, Licht: Fi 13, Fi-Bu 14, Bu 16) und der Lichtdaten im Flachland (Dgl 11, Dgl-Bu 11, Bu 9, Kie 9, Kie-Bu 14), Flächengröße 400 m². Unterschiedliche Buchstaben kennzeichnen signifikante Unter- schiede (Kruskal-Wallis-Test, p < 0.05).

4 Discussion who compared pure Douglas-fir with mixed stands, found no significant differences concerning diversity. As for the Norway Questions about the improvement of the status for nature spruce comparison, the influence of beech on diversity is often conservation and by admixture of beech in coniferous not considerable until the beech fraction is clearly dominant stands are, strictly speaking, questions about how ecological (Le i t l 2002). Plant species numbers, as well as coverage of interactions meet the aims of silviculture or nature conserva- vegetation layers, of mixed and pure spruce stands in the tion. Both agree on fundamental assumptions concerning the Solling Mountains do not differ significantly. Nevertheless, preservation of biological diversity and increasing natural- other authors were able to observe clear relationships where ness of forests. Although the connection between diversity mixed stands always have a medium position (Lü c k e & Sc h m i d t and ecosystem functions is not yet known in detail (Sc h u l z e 1997, Ma t t h e s 1998, En g e l h a r d & Re i f 2004, Sc h m i d t et al. & Mo o n e y 1993, Lo r e a u et al. 2002, Sc h e r e r -Lo r e n z e n et al. 2004, Ba r b i e r et al. 2008). 2005, Le u s c h n e r et al. 2009), it is a commonly held opinion, that biodiversity increases ecosystem stability (Su k o p p & Tr e p l As far as naturalness of herb layer is concerned, in Douglas-fir 1987, Fü h r e r 2000, Sc h m i d t 2006, Pa q u e t t e & Me ss i e r 2011). and Scots pine comparisons the highest percentage of typical Changes in forest tree species composition and structure forest plants is reached in the mixed stands. Only the Norway inevitably lead to changes in the biodiversity of forest-dwelling spruce comparison shows a continuous relative increase of species. A meta-analysis by Pa i ll a t et al. (2010) shows that typical forest species from pure spruce over mixed up to pure diversity of some taxa is more affected by forest management beech stands. Lü c k e & Sc h m i d t (1997), Le i t l (2002), Gä r t n e r than others. Our study only highlights one component, the (2003) and Sc h m i d t et al. (2004) also found in their vegetation understorey vegetation with vascular plants and soil-dwelling studies an increasing naturalness with increasing beech frac- bryophytes, well aware that results may be different if including tion. But, similarly to the results of the present study, Lü c k e species like epiphytic lichens, fungi, birds or insects. & Sc h m i d t (1997) point out that the absolute number of forest species is decreasing with an increasing beech fraction. Based 4.1 Diversity and naturalness on the potential occurrence of plant species in close-to-nature beech forests Sc h m i d t et al. (2004) also confirm a continuous The results generally show a decreasing species diversity increase of naturalness with the conversion of Scots pine from conifer stands towards beech stands. Clear gradients stands into beech stands. of diversity, in comparable Scots pine admixtures, are also found by Sc h m i d t et al. (2004) or Vo r & Sc h m i d t (2006). Com- The claim for both more diversity and more naturalness parisons of the diversity of Douglas-fir stands with mixed often means a conflict on a local scale in regions where one stands or beech stands are rare and results are varying would expect the Luzulo-Fagetum to be the potential depending on the research area and site conditions. While natural vegetation. These forests show very low numbers of studies from Ze r b e (1999) in the Spessart Mountains coincide plant species in general and therefore, diversity increases with the present results, Kn o e r z e r & Re i f (1996) observed due to enrichment or conversion with non site-specific tree the opposite in the . Both studies only compared species. Relationships between increasing number of plant pure stands of Douglas-fir with beech.V o r & Sc h m i d t (2006), species and anthropogenic influence have been noticed by

Waldökologie, Landschaftsforschung und Naturschutz 11 (2011) 55 AFSV Biodiversitäts-Forschung

several authors. We c k e ss e r (2003) and Fr i t z (2006) describe every tree species produces typical light conditions which increased species diversity of artificial coniferous forests as are more or less independent from silvicultural management a direct effect of human impact. The studies of De t s c h (1999), (Mi t s c h e r l i c h 1981, Me ss i e r et al. 1998, Ha g e m e i e r 2002, Fr e c h Oh e i mb et al. (1999), Sc h m i d t (1999, 2005), We s t p h a l (2001) 2006, Mö l d e r et al. 2008, Ell e n b e r g & Le u s c h n e r 2010). On and Sc h m i d t & Sc h m i d t (2007) as well as a meta-analysis on the other hand, light conditions at stand level are highly influ- European forests (Pa i ll e t et al. 2010) document higher vas- enced by silvicultural impacts, which again may be typical for cular plant species diversity in managed forests compared each tree species. In Lower Saxony, the silviculture follows with unmanaged forests. the guidelines of the LÖWE program (Long term program for Diversity does not necessarily mean naturalness, depending ecological-orientated forest management, Ni e d e r s ä c h s i s c h e a n d e s f o r s t e n very much on the spatial scale used (An d e r s & Ho f m a n n 1997, L 2011). This means that harvesting methods St a n d o v á r et al. 2006). Hence Fr i t z (2006) points out, that for do not differ between stand types because trees are always the postulation of more diversity it is important to observe a single-tree- or group-selected. Differences therefore can arise wider area than only one stand. At the landscape level, the due to stand structure, which mainly depends on stand history. conflict between diversity and naturalness recovers because of Investigated beech stands often have a more differentiated age different stand types. At least concerning the gamma-diversity distribution because they have been naturally regenerated for of this study, defined as cumulative species richness per stand some decades while conifers were planted and even-aged. type, naturalness and diversity remain contrary. To mix differ- Likewise, top soil quality is affected by the tree species, ent stand types with a clearly distinct naturalness may not be especially acidification through conifer trees (Spruce: Ze r b e convincing in this context. 1994, Hü t t l & Sc h a a f 1995, Lü c k e & Sc h m i d t 1997; Douglas-fir: Ma r q u e s & R a n g e r 1997). Humus accumulation (Fi s c h e r et al. With regard to higher naturalness, it is important to differenti- 2002, Ka u t z & To p p 1998) and C/N-ratio (Lü c k e & Sc h m i d t 1997, ate between natural and artificial diversity (Di e r ss e n & Ki e h l Zh o n g & Ma k e s c h i n 2004) change as well with the introduction 2000, Sc h m i d t et al. 2003). Therefore mixed forests should be of trees into conifer stands. Forest management promoted first of all to their natural habitats, e. g. the transition zone between broadleaves and conifers in mountainous areas. also has been shown to influence soil fertility A( u g u s t o et al. Furthermore, mixed forests are also important regarding the 2002). However, even if the use of harvesting machines is uncertainty of future climate trends and the long-term perspec- more common in conifer stands than in beech stands, there tive which is necessary for stand conversion. Considering should not be any difference in soil disturbance because the economical aspects, Lü p k e & Sp e llm a n n (1999) highlight the machines should stay on strictly defined skidding tracks. positive impact of beech on pure spruce stands, because beech is less sensitive to environmental disturbances and therefore The effect of beech introduction on understorey vegetation in reduces economic risks. Even so, an absolute exclusion of pure conifer stands is therefore indirectly measurable in terms spruce would result in noticeable profit cuts because of the of light and soil conditions. Light conditions clearly play a major higher productivity of spruce (Pr e t z s c h & Sc h ü t z e 2005). role, especially concerning coverage of understorey vegetation, e. g. We i sb e r g et al. (2003) found a greater influence from light 4.2 Similarity and site conditions conditions on coverage than on plant species diversity. While plant species diversity and naturalness show more or 5 Conclusion less consistent trends for all three comparisons, with a decreas- ing diversity and an increasing naturalness due to admixture To address the issue of the improvement of conifer stands of beech, similarity highlights the differences between them. through beech, first of all it is important to declare objectives Both the admixture with Douglas-fir and Norway spruce seem concerning their status for nature conservation and forestry. to change species composition relatively slowly, with the Assuming that these objectives are promotion or preserva- mixed stands still having a higher similarity towards the pure tion of a natural diversity, measured by the potential natural coniferous than the pure beech stands. For Norway spruce vegetation of the Luzulo-Fagetum, beech clearly has this is confirmed byL e i t l (2002) and Fr i t z (2006). In contrast, a positive impact on artificial conifer forests. Depending on mixed stands with pine and beech are scarcely distinguishable the conifer tree species, the effects are different. While mixed from pure beech stands, which means that Scots pine stands stands of pine and beech are hardly distinguishable from are ecologically more sensitive to conversion with beech. In pure beech stands, in terms of species diversity or vegetation this regard, Sc h m i d t (2007) refers to European beech as an structure, mixed spruce-beech stands show a higher similarity “Ecosystem engineer” because physical and chemical site towards pure spruce stands. Douglas-fir-beech stands range in conditions change strongly by replacing coniferous trees with European beech. However, a qualitative change of the species between, with a greater similarity to the pure beech stands. pool does not take place. Almost all species occurring in pure beech stands are also found in the mixed and pure coniferous Acknowledgements stands enriched by typical species of coniferous forests. This Andrea Bauer, Heiko Rubbert and Andreas Parth were a great could be understood that not only tree species composition itself is an important factor for understorey species composi- help during the fieldwork and the analysis of soil samples and tion, but also the homogenous site conditions characterizing data. Special thanks to Steffi Heinrichs for helpful sugges- the Luzulo-Fagetum as potential natural vegetation. tions that improved the manuscript and to two anonymous Au g u s t o et al. (2003) even found a lower impact from tree reviewers and the editor Michael Manthey for their valuable species on understorey vegetation in comparison with the comments. We are grateful to Ginamarie Lopez and Ruth impact from site conditions and silvicultural management. In Gilbert for language correction. This research was supported fact there is no consensus about the effect of different tree by the German Science Foundation (DFG, grant number Schm species on understorey vegetation (Lü c k e & Sc h m i d t 1997, 319/13) and the German Federal Ministery of Education and Ew a l d 2000, Au g u s t o et al. 2002, 2003). On the one hand, Research (BMBF).

56 Waldökologie, Landschaftsforschung und Naturschutz 11 (2011) Biodiversitäts-Forschung AFSV

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Wi ss k i r c h e n , R., Ha e u p l e r , H. (1998): Standardliste der Farn- und Blütenpflanzen Deutschlands. Ulmer, Stuttgart: 765 pp. Wo l f f , B., Er h a r d , M., Ho l z h a u s e n , M., Ku h l o w , T. (2003): Das Klima in den Forstlichen Wuchsgebieten und Wuchsbezirken Deutschlands. Mitt. Bundesforsch.anst. Forst- Holzwirtsch. 211: 29 pp. Ze r b e , S. (1999): Die Wald- und Forstgesellschaften des Spes- sarts mit Vorschlägen zu deren zukünftigen Entwicklung. Mitt. naturwiss. Mus. Aschaffenburg 19: 3-354. Ze r b e , S., Br a n d e , A., Gl a d i t z , F. (2000): Kiefer, Eiche und Buche in der Menzer Heide (N-Brandenburg) – Veränderun- gen der Waldvegetation unter dem Einfluß des Menschen. Verh. Bot. Ver. Berlin Brandenburg 133: 45-86. Ze r b e , S. (1994): Vegetations- und Strukturveränderungen in Fichtenforsten im Vergleich zu Hainsimsen-Buchenwäldern als Ausdruck ökologischer Instabilität. Verhandl. Ges. Ökol. 23: 191-196. Zh o n g , Z., Ma k e s c h i n , F. (2004): Comparison of soil nitrogen dynamics under beech, Norway spruce and Scots pine in central Germany. Eur. J. Forest Res. 123: 29 -37. submitted: 15.03.2011 reviewed: 19.05.2011 accepted: 25.08.2011

Adresses of authors: Dr. Sabine Budde (corresponding author) Email: [email protected] Prof. Dr. Wolfgang Schmidt Email: [email protected] Dr. Martin Weckesser Email: [email protected] Georg-August-Universität Göttingen, Fakultät für Forst- wissenschaften und Waldökologie, Burckhardt-Institut, Abteilung Waldbau und Waldökologie der Gemäßigten Zonen Büsgenweg 1, D-37077 Göttingen

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Appendix / Anhang

Tab. 3: Plant species of herb and moss layer (*: Hypnum cupressiforme includes H. jutlandicum in the lowland stands). Absolute frequency (F) and coverage (C, mean %, 0.0 = ≤ 0.05 %), n = 20, plot size = 400 m2. r = Pearson correlation with the first order axis of the DCA matrix. Only species reaching r ≥ 0.33 or at least a frequency of ten in one stand type are included.

Tab. 3: Arten der Kraut- und Moosschicht(*: im Tiefland wurden H. cupressiforme und H. jutlandicum zusammengefasst). Absolute Häu- figkeit (F) und Deckungsgrad (C, prozentuales Mittel, 0.0 = ≤ 0.05 %), n = 20, Aufnahmefläche = 400 m². r = Pearson-Korrelation mit der 1. Achse der DCA-Matrix. Nur Arten mit r ≥ 0.33 oder einer Häufigkeit von mindestens 10 in einem Bestandestyp wurden berücksichtigt.

Douglas-fir Norway spruce Scots pine Dou Mix Be Spr Mix Be Pi Mix Be r

Herb layer F C F C F C F C F C F C F C F C F C

Predominantly in conifer stands Deschampsia flexuosa 17 0.9 12 0.2 5 1.0 19 2.3 17 3.3 5 0.0 20 43.8 7 0.1 5 1.0 -0.76 Vaccinium myrtillus 19 1.2 8 0.0 - - 18 1.7 14 0.2 - - 20 48.8 7 4.0 - - -0.73 Dryopteris carthusiana 6 0.0 8 0.0 4 0.0 10 0.0 17 0.0 8 0.0 20 0.8 5 0.0 4 0.0 -0.49 Sorbus aucuparia 19 0.1 15 0.0 6 0.0 20 0.0 20 0.0 8 0.0 15 0.1 11 0.0 6 0.0 -0.48 Dryopteris dilatata 20 12.7 17 2.8 10 0.0 20 1.2 19 0.6 11 0.0 19 1.4 5 0.2 10 0.0 -0.35 Quercus spec. 12 0.0 8 0.0 6 0.0 3 0.0 2 0.0 - - 19 0.1 10 0.0 6 0.0 -0.60 Rubus idaeus 11 6.6 10 1.1 2 0.0 13 0.0 12 0.5 8 0.6 19 15.2 3 0.0 2 0.0 -0.42 Galium saxatile 7 0.0 3 0.0 - - 19 0.2 16 0.1 - - 12 0.5 - - - - -0.33 Epilobium angustifolium 8 0.0 1 0.0 2 0.0 17 0.1 12 0.0 1 0.0 13 0.0 1 0.0 2 0.0 -0.38 Trientalis europaea 11 0.2 6 0.0 - - 15 0.1 4 0.0 - - 16 1.0 1 0.0 - - -0.52 Pseudotsuga menziesii 15 0.1 11 0.0 1 0.0 ------1 0.0 - 0.17 Agrostis capillaris 5 0.0 1 0.0 1 0.0 15 0.0 10 0.3 8 0.0 3 0.0 - - 1 0.0 0.09 Rubus fruticosus agg. 13 0.1 5 0.0 4 0.0 3 0.0 9 0.1 3 0.0 12 0.5 4 0.0 4 0.0 -0.44 Pinus sylvestris 2 0.0 1 0.0 2 0.0 ------10 0.0 - - 2 0.0 -0.51 Calluna vulgaris 1 0.0 ------10 0.1 - - - - -0.48 Frangula alnus 6 0.0 7 0.0 3 0.0 - - 1 0.0 - - 10 0.0 4 0.0 3 0.0 -0.47 Betula spec. 10 0.0 5 0.0 3 0.0 1 0.0 - - - - 6 0.0 - - 3 0.0 -0.41 Ceratocapnos claviculata 8 0.2 3 0.1 2 0.0 ------8 0.5 2 0.0 2 0.0 -0.44 Predominantly in beech stands Fagus sylvatica 8 0.0 20 0.3 19 3.1 8 0.0 19 2.2 20 7.1 - - 18 0.4 19 3.1 0.62 Indifferent Luzula luzuloides ------17 0.0 20 0.6 16 0.7 ------0.38 Carex pilulifera 19 0.2 12 0.0 13 0.0 19 0.1 20 0.0 14 0.1 5 0.0 1 0.0 13 0.0 0.12 Oxalis acetosella 10 6.8 9 1.4 2 2.3 10 1.8 17 7.5 12 2.3 1 0.0 6 0.3 2 2.3 0.28 Athyrium filix-femina 4 0.2 - - - - 6 0.1 15 0.0 3 0.0 - - 1 0.0 - - 0.14 Juncus effusus 7 0.0 3 0.0 1 0.0 8 0.0 12 0.0 8 0.0 1 0.0 - - 1 0.0 0.11 Cardamine flexuosa 4 0.0 1 0.0 2 0.0 8 0.0 10 0.0 4 0.0 - - - - 2 0.0 0.21 serotina 3 0.0 7 0.0 2 0.0 ------2 0.0 3 0.0 2 0.0 -0.31 Moss layer Predominantly in conifer stands Hypnum cupressiforme* 19 8.9 15 0.5 11 0.0 10 0.5 18 0.0 11 0.0 20 26.6 11 0.1 11 0.0 -0.69 Pleurozium schreberi 13 0.1 - - - - 6 0.0 3 0.0 - - 20 29.7 2 0.0 - - -0.69 Dicranum scoparium 20 0.2 8 0.1 14 0.0 16 0.3 16 0.1 1 0.0 18 2.7 12 0.1 14 0.0 -0.61 Plagiothecium laetum var. ------13 1.1 19 0.1 1 0.0 ------0.13 curvifolium Eurhynchium praelongum 17 5.0 6 0.0 1 0.0 8 0.0 4 0.0 1 0.0 11 0.7 - - 1 0.0 -0.30 Lophocolea bidentata 1 0.0 1 0.0 - - 9 0.3 - - - - 15 0.1 2 0.0 - - -0.46

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Scleropodium purum 11 1.5 1 0.0 ------10 4.4 - - - - -0.42 Predominantly in beech stands Pseudotaxiphyllum elegans - - - - 2 0.0 - - 3 0.0 9 0.0 - - - - 2 0.0 0.36 Indifferent Polytrichum formosum 20 6.3 17 0.5 15 0.1 20 3.3 20 5.0 19 0.4 17 1.6 12 0.3 15 0.1 - 0.12 Herzogiella seligeri 1 0.0 2 0.0 4 0.0 14 0.1 20 0.1 1 0.0 - - 7 0.1 4 0.0 0.14 Brachythecium rutabulum 15 7.8 9 0.6 13 0.0 15 0.2 19 0.3 9 0.0 18 7.5 9 0.2 13 0.0 -0.35 Mnium hornum 13 1.4 11 0.0 13 0.0 10 0.5 15 0.1 5 0.0 - - 3 0.0 13 0.0 0.10 Atrichum undulatum 13 0.1 7 0.0 8 0.0 5 0.0 6 0.0 5 0.0 - - 3 0.0 8 0.0 0.18

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